Background: Asthma associated with sinusitis is supposed to be sustained by bronchoconstrictive reflexes originating in extrathoracic airway (EA) receptors.
Objective: The study was designed to evaluate the relationship between EA responsiveness and bronchial responsiveness in sinusitis.
Methods: We performed histamine inhalation challenge in 106 patients with chronic sinusitis, during disease exacerbation and after treatment with antimicrobials and nasal flunisolide (100 micrograms daily) for 2 weeks. Forced expiratory volume in 1 second (FEV1) and maximal mid-inspiratory flow (MIF50) were the respective indexes of bronchial and EA narrowing; the histamine concentrations causing a 20% fall in FEV1 (PC20) and 25% drop in MIF50 (PC25MIF50) were used as thresholds of bronchial and EA responsiveness. Thresholds of 8 mg/ml or less were assumed to indicate bronchial hyperresponsiveness (B-HR) or EA hyperresponsiveness (EA-HR).
Results: During sinusitis exacerbation 76 patients had EA-HR, which in 46 was associated with B-HR. The values of PC20 were closely related with those of PC25MIF50 (p < 0.001). EA-HR and B-HR were strongly associated with pharyngitis. After treatment, mean PC25MIF50 and PC20 were significantly increased (p < 0.001). The improvement of PC25MIF50 was closely related to that of PC20 (p < 0.001) and to the decrease in neutrophils in nasal lavage (p < 0.05). EA-HR reversed in 58 patients and improved in 10; B-HR reversed in 29 and improved in 12.
Conclusions: Our findings suggest that in sinusitis, B-HR may be sustained by constrictive reflexes originating in pharyngeal receptors, made hypersensitive by seeding of the inflammatory process.